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Abstract

Physiological tissue dynamics following breast compression offer new contrast mechanisms for evaluating breast health and disease with near infrared spectroscopy. We monitored the total hemoglobin concentration and hemoglobin oxygen saturation in 28 healthy female volunteers subject to repeated fractional mammographic compression. The compression induces a reduction in blood flow, in turn causing a reduction in hemoglobin oxygen saturation. At the same time, a two phase tissue viscoelastic relaxation results in a reduction and redistribution of pressure within the tissue and correspondingly modulates the tissue total hemoglobin concentration and oxygen saturation. We observed a strong correlation between the relaxing pressure and changes in the total hemoglobin concentration bearing evidence of the involvement of different vascular compartments. Consequently, we have developed a model that enables us to disentangle these effects and obtain robust estimates of the tissue oxygen consumption and blood flow. We obtain estimates of 1.9±1.3 µmol/100mL/min for OC and 2.8±1.7 mL/100mL/min for blood flow, consistent with other published values.

Representative hemodynamic measurement. An initial decrease in blood volume and a small decrease in saturation are observed during the initial compression, followed by a slow increase in blood volume and a continued decrease in saturation. Data from three subjects is presented, with the total hemoglobin [HbT] trace on the left, followed by the hemoglobin saturation time course, and finally, the compression force needed to maintain the position of the compression plates on the right.

Total hemoglobin concentration vs pressure plots from three subjects, showing lower apparent compliance at high pressure and higher apparent compliance at lower pressures. Data is taken from measurements performed on the same volunteers shown in Figure 2.

Table 5. Summary of metabolic parameters estimated from measurements satisfying the inclusion criteria listed above, using, respectively, the model in Ref. 24 (Carp2006) and the metabolic model described in §2.4 including the blood volume correction described in the beginning of the current section

Metrics

Table 1.

[HbT] decrease during compression and subsequent recovery during tissue relaxation

Cycle 1

Cycle 2

Cycle 3

[HbT] initial decrease

14.3±7.4%

17.7±3.8 %

19.3±2.5 %

[HbT] recovery

7.4±11.5 %

3.8±4.7 %

2.53±4.2 %

Table 2.

Pressure relaxation characteristics

Cycle 1

Cycle 2

Cycle 3

Fast pressure relaxation

17.9±9.0 %

18.7±7.4 %

18.5±10.0 %

Slow pressure relaxation

43.2±12.1 %

28.9±7.6 %

28.6±10.9 %

Percentage of total relaxation during fast drop

27%

40%

40%

Table 3.

Pressure relaxation dynamics

Cycle 1

Cycle 2

Cycle 3

Duration of quick decrease

3s

3s

3s

Decay time constant of slow decrease

29.5±9.8s

37.5±8.2s

46.2±17.8s

Table 4.

Metabolic analysis criteria summary

Cycle 1

Cycle 2

Cycle 3

Overall

Accepted for analysis

8 (18.2%)

9 (20.5%)

11 (25.0%)

28 (21.2%)

Rejected due to SO2 SNR

29 (65.9%)

25 (56.8%)

25 (56.8%)

79 (59.9%)

Rejected due to ∂2SO2,corr/dt2<0

16 (36.4%)

18 (40.9%)

14 (31.8%)

48 (36.4%)

Rejected due to [HbR] increase while compressing

11 (25.0%)

12 (27.3%)

9 (20.5%)

32 (24.2%)

Rejected due to data artifacts

6 (13.6%)

10 (22.7%)

4 (9.1%)

20 (15.2%)

Table 5.

Summary of metabolic parameters estimated from measurements satisfying the inclusion criteria listed above, using, respectively, the model in Ref. 24 (Carp2006) and the metabolic model described in §2.4 including the blood volume correction described in the beginning of the current section

Cycle 1

Cycle 2

Cycle 3

(Method in Carp2006) Oxygen Consumption (µmol/100mL/min)

5.44±6.39

7.54±7.98

3.30±4.79

(Method in ੲ2.4) Oxygen Consumption (µmol/100mL/min)

1.65±0.73

2.11±1.89

1.89±1.27

(Method in Carp2006) Blood Flow (ml/100mL/min)

9.57±11.15

8.20±9.21

4.65±5.73

(Method in ੲ2.4) Blood Flow (ml/100mL/min)

2.67±1.28

2.97±2.18

2.78±1.70

(Method in Carp2006) R2

0.61

0.49

0.74

(Method in ੲ2.4) R2

0.88

0.90

0.93

Tables (5)

Table 1.

[HbT] decrease during compression and subsequent recovery during tissue relaxation

Cycle 1

Cycle 2

Cycle 3

[HbT] initial decrease

14.3±7.4%

17.7±3.8 %

19.3±2.5 %

[HbT] recovery

7.4±11.5 %

3.8±4.7 %

2.53±4.2 %

Table 2.

Pressure relaxation characteristics

Cycle 1

Cycle 2

Cycle 3

Fast pressure relaxation

17.9±9.0 %

18.7±7.4 %

18.5±10.0 %

Slow pressure relaxation

43.2±12.1 %

28.9±7.6 %

28.6±10.9 %

Percentage of total relaxation during fast drop

27%

40%

40%

Table 3.

Pressure relaxation dynamics

Cycle 1

Cycle 2

Cycle 3

Duration of quick decrease

3s

3s

3s

Decay time constant of slow decrease

29.5±9.8s

37.5±8.2s

46.2±17.8s

Table 4.

Metabolic analysis criteria summary

Cycle 1

Cycle 2

Cycle 3

Overall

Accepted for analysis

8 (18.2%)

9 (20.5%)

11 (25.0%)

28 (21.2%)

Rejected due to SO2 SNR

29 (65.9%)

25 (56.8%)

25 (56.8%)

79 (59.9%)

Rejected due to ∂2SO2,corr/dt2<0

16 (36.4%)

18 (40.9%)

14 (31.8%)

48 (36.4%)

Rejected due to [HbR] increase while compressing

11 (25.0%)

12 (27.3%)

9 (20.5%)

32 (24.2%)

Rejected due to data artifacts

6 (13.6%)

10 (22.7%)

4 (9.1%)

20 (15.2%)

Table 5.

Summary of metabolic parameters estimated from measurements satisfying the inclusion criteria listed above, using, respectively, the model in Ref. 24 (Carp2006) and the metabolic model described in §2.4 including the blood volume correction described in the beginning of the current section